Mechanical underfeed stoker



March 17, 1936. E. c. 'SEVELLEC 2,034,448

MECHANICAL UNDERFEED STOKER Filed No v. 1,1933 5 Sheets-Sheet 1 NveNT R [Hwy E. C- eve ea March 17, 1936.

E. c. SEVELLEC MECHANICAL UNDERFEED STOKER s Sheets-Shet 2 Filed Nov. '1, 1953 5 C 5 we [la Q [:vveNToR W 4' dwhj l I March 17, 1936. E. c. SEVELLEC 2,034,448

MECHANICAL UNDERFEED STOKER Filed Nov. 1, 1933 3 Sheets-Sheet 3 l ycN R Patented Mar. 17, 1936 UNITED STATES PATENT ()FFIE 2,034,443 MECHANICAL UNDERFEED s'roKEn Eugene Cyprien Svellec, Neuilly-sur-Seine,

France 3 Claims. (01. 110-45) This invention refers to improvements in or relating to mechanical underfeedstokers, wherein the fuel is fed to'the furnace from below in such a manner as to ensure the complete burning 5 of any solid or pasty fuel therein and to ensure a perfect and automatic mechanical operation and combustion by means of an air blast and stoking at the very centre of the incandescent fuel mass.

To enable the invention to be more clearly understood it is hereafter more specifically described by way of example, with reference to the accompanying drawings which show one embodiment of the present invention as adapted to an ordinary furnace of a rectangular section, and in which:

Fig. 1 shows a longitudinal section of a hearth or furnace of rectangular section having an underfeed stoking device and provided with a bottom and top air blast and comprising mechanical stokers or pokers which are cooled by means of the current of the air blast,

Figure 2 is a plan view thereof.

Figure 3 shows a section taken on the line A-A 25 of Figure 1.

Figure 4 is a section taken on the line 3-3 of Figure 1;

Figure 5 is a section taken on the line C0 of Figure 1; 30 Figure 6 shows a constructional form with a circular furnace or hearth provided with mechanical stokers or pokers;

Figure 7 shows a constructional form with a circular fire pot but not provided with mechani- 35 calstokers or pokers;

Figure 8 shows a constructional form of a circular fire pot with a central air blast nozzle and aquadruple airinlet;

Figure 9 is an end view of a bottom nozzle or the like comprising a poker of a sinusoidal shape and Figure 10 represents an end view of a bottom air blast nozzle or the like subdivided by partitions.

Referring to Figures '1 and 2 of the drawings, a motor or engine I of any suitable type transmits motion by means of a belt 2' to a speed reducing gear 3 and also drives by means of a belt 2 a blower or fan 4 of a standard type producing the blast air. The speed reducing gear 3 transmits its rotary motion to an endless conveyor screw 5 by means of a coupling shaft 6 passing through the lower portion of the housing of the blower or fan 5. The endless conveyor or screw 5 passes through a chest or bucket mounted beneath a fuel feed hopper H which chest or bucket is extended forwardly in the form of a conduit I which encloses the conveyor or screw circumferentially, the said conveyor screw extending into the fire pot 8. A wheel 20 mounted 5 in the hopper I9 is provided with stirrerswhich continuously stir up the mass of fuel therein to ensure a uniform fuel feed to the vanes of the conveyor screw 5. The stirrer wheel 20 is rotated by means of a suitable transmission gear driven 10 by the speed reducing gear 3. Two shafts 9 and 9' extend from the speed reducing gear box 3,

in a direction parallel to the conveyor screw 5, as shown in Figure 2 and are rotated by means of pinions or chain gears. These shafts 9 and 9' carry on their free extremities cams or cranks l0 and I0 which cause coupling bars or rods I l--I I to rise and recede. On these coupling bars or rods H and II are mounted pokers l2 and I! which slide within tubular members or the like I3 and I3 respectively provided in the wall of the fire pot 8.. Regulating vanes or louvres l4 and M are so mounted on one side of the tubular members or the like l3 and I3 as to ensure that the air blast is"distributed to a greater amount to the bottom tubular members than to the other air blast orifices provided in the fire pot. The conduit I having mounted therein the endless conveyor screw 5 for conveying the fuel to the fire pot 8 is mounted within a housing 2| which completely surrounds the conduit 7 and which is connected at one end thereof to the discharge end of the blower or fan- 4 and at the other end to the fire pot 8. Thus the air blast from the blower or fan 4 is fed directly into the fire pot 8 from where it passes on through the bottom ducts or the like l3 and I3 and the top air blast orifices, which are disposed peripherally and through the layer of the fuel on the fire pot.

It will of course be clearly understood that the speed of rotation of the shafts 9 and 9' and the displacement of the bars II and II is so calculated as to ensure a suflicient effect on the pokers l2 and I2 in the mass of burning fuel so that the air blast can penetrate freely through the fire pot B-irrespeetive of the cohesive power of the fuel used. In this arrangement of the fire pot 8 the air is injected annularly through peripheral top holes, as is the case in other known systems but this air admission is in fact of secondary importance, the really important and highly efficient air admission taking place through the central tubular members or the like l3 and I3 designed for a large volumedischarge, there being 3 or 4 such tubular members or the like provided. There is thus obtained a perfectly uniform combustion of thefuel on the whole of the surface of the fire pot whereas the other hitherto known systems give an intense combustion near the annular openings, but the central part of the fire does not burn.

In fact if fiaming small coal is being burnt the automatic burners with annular blast function nearly normally but with lean smalls, or with lean fine coal, /10, l4, or fully fatty coal it becomes an absolute necessity to use central tubular members also. Moreover the permeability of a fuel layer is apt to vary according to whether fine coal having a variable content of volatile matter or fatty coal is being used. So as to make the permeability of the fuel layer perfectly constant and uniform the rods I2 and I2 which pass through the central tubular members or the like l3 and I3 and operated by means of the cams l0 and I 0 work the fuel up in a predetermined sense and a permanent working of the layer of fuel which is thus lifted on the whole of its surface at different times. It thus becomes possible for the mass of coal to breath on the grate, the air passing much more easily through the layer and at a constant rate. The bottom tubular members or the like l3 and I3 may have sections such as those shown in Figures 9 and 10.

In the arrangement according to Figure 9 the rods I 2 shown therein displaced in the tubular members may have a sinusoidal shape, making it possible to constitute a veritable grate surface which opposes itself to the passage of the fuel, whatever may be its size, the air blast passing through the undulations of the said rod. The tubular member shown on Figure does not require any pokers and the air is suitably distributed by means of partitions I3 The electric motor may be suitably and automatically controlled and the automatic control may be actuated by the apparatus to be heated or by the exhaust gases and all the automatic controls of the different elements may be actuated simultaneously and at a speed which is proportional to the speed of the conveyor screw by means of acting on the speed regulating device 3, and the quantity of air discharged by the fan 4 may also be regulated by varying its speed or by reducing the cross-sectional area of the air intake of the fan, by means of suitably mounted louvres or the like. Moreover, if desired, there may be added to the pokers l2 and I2 displaceably mounted in the bottom tubular members I 3 and I3, further pokers suitably mounted in the top blast tubes in such a number that the desired effect is fully attained.

The fire pot shown in Figure 6 is of a circular shape and has bottom tubular members or the like l3 and I3 through which the pokers l2 and I2 pass, which are actuated in a manner similar to that described above. The fire pot shown in Figure 7 is also of a circular shape and. also has bottom tubular members l3 and I3 but there are no pokers provided, the section of the tubular members being as shown in Figure 10 and comprising partitions I3 Finally, the fire pot shown in Figure 8 is also of a circular shape and comprises a central tubular member l6 and the air blast admission orifices H for the admission of the air from the fan.

I claim:

1. A mechanical underfeed stoker comprising a furnace having a fire pot for receiving a mass of coal, a screw conveyor for feeding the fuel into the lower part of said fire pot, a conduit containing said screw conveyor, a fuel storage hopper for discharging fuel into said conduit, a fan for generating an air blast, a housing spaced about said fire pot and providing an air chamber therebetween, means providing communication between said chamber and said fan, tubular members extending upwardly fromthe inner walls of said fire pot and converging toward the central part of the fire pot for receiving said air blast and discharging it into the middle of the coal mass, operating means for driving said conveyor and said fan, and pokers reciprocably mounted in said tubular members for breaking up the burning fuel layer, said pokers being of less cross-sectional area than the tubular members to permit the air to pass through the tubular members, and said operating means also acting to reciprocate the pokers.

2. A mechanical underfeed stoker, comprising a fire pot, a fuel storage hopper, a conduit extending from the bottom of the hopper to and in communication with the lower part of the fire pot, feeding means in the conduit for advancing fuel from the hopper to the fire pot, a housing spaced around the lower part of the fire pot and the conduit and forming an air chamber thereabout, a fan in communication with the chamber for directing an air blast therethrough, a series of upwardly inclined air tubes projecting from the lower part of the fire pot and converging toward the central middle part thereof for receiving air from the chamber and discharging it into the middle of the coal mass near the top thereof, pokers reciprocably mounted in said tubes for breaking up the burning fuel mass and being of less cross-sectional area than the tubes to permit the air to pass through the tubes, and common means for synchronously operating the feeding means, the fan, and the pokers.

3. A stoker as claimed in claim 2, wherein the fire pot is provided with lateral openings positioned above the upper ends of the tubes for passing an air blast horizontally into the fuel mass.

EUGENE CYPRIEN sii'vnmnc. 

